1. Field of the Invention
This invention relates to a novel di- or triphenyl monoterpene hydrocarbon derivative useful as a dissolution rate regulator and a chemically amplified positive resist composition containing the same and suitable for use in fine patterning.
2. Prior Art
As the LSI technology tends toward higher integration and higher speed, further refinement of pattern rules is required. The current patterning technology mostly relies on light exposure which is now approaching to the essential limit of resolution which is dictated by the wavelength of a light source. It is generally recognized that in light exposure using g-line (wavelength 436 nm) or i-line (wavelength 365 nm) as a light source, a pattern rule of about 0.5 .mu.m is the limit. For LSIs fabricated by such light exposure technique, a degree of integration equivalent to 16 mega-bit DRAM is the limit. At present, LSIs fabricated in the laboratory have reached this stage. It is urgently required to develop a finer patterning technique.
Under such circumstances, deep-ultraviolet lithography is regarded promising as the next generation of fine patterning technology. The deep-UV lithography is capable of working on the order of 0.3 or 0.4 .mu.m and makes it possible to form a resist pattern having a side wall nearly perpendicular to the substrate if a less light absorbing resist material is used. Advanced engineers place focus on the utilization of high illuminance KrF excimer laser as a deep-UV source. A resist material having low light absorption and high sensitivity must be developed before such an excimer laser can be used in a mass scale manufacturing technique.
From this point of view, a number of chemically amplified positive working resist materials using acid catalysts were recently developed as disclosed in JP-B 27660/1990, JP-A 27829/1988, U.S. Pat. Nos. 4,491,628 and 5,310,619. These materials have high sensitivity, resolution and dry etching resistance and are promising as resist materials especially suited for deep-UV lithography.
It is known that the function of chemically amplified positive resist material is largely governed by a dissolution rate regulator or inhibitor used therein. There are known a number of dissolution inhibitors while those having enhanced dissolution inhibiting ability are (i) compounds having at least two acid labile groups wherein the acid labile groups at the remotest positions are intervened by at least 10 linking atoms excluding the acid labile groups and (ii) compounds having at least three acid labile groups wherein the acid labile groups at the remotest positions are intervened by at least 9 linking atoms excluding the acid labile groups as disclosed in JP-A 266109/1994. Exemplary such compounds are shown below by formulae (3a) and (3b). ##STR2##
The aforementioned compounds themselves are lipophilic and have the above-mentioned properties. When blended as a resist component, a dissolution inhibitor of this type acts to reduce the solubility of the resist material in aqueous alkali solution thus preventing the resist film from thinning upon development. In exposed areas, an acid is generated to eliminate the acid labile group from the dissolution inhibitor so that the exposed areas become soluble in aqueous alkali solution. In this way, the same dissolution inhibitor acts to increase the dissolution rate of exposed areas.
However, chemically amplified positive resist compositions using the aforementioned compounds as a dissolution rate regulator fail to provide high resolution upon alkali development. This is probably because the compounds have greater light absorption in the deep-UV region. When a chemically amplified positive resist composition containing the same is used in deep-UV lithography, it is difficult to form a pattern having a side wall perpendicular to the substrate. As a consequence, high resolution is not expected. An improvement in this respect is thus desired.